1. Field
The present invention relates generally to radar systems, and, in particular, to radar systems having dual modes, and still more particularly, to radar systems having a weather radar mode and an air surveillance mode.
2. Description of the Related Art
Since the invention of detection and ranging using radio frequencies, different radar systems have been developed to meet the requirements of detecting different phenomena or objects. All radars work on the same basic principles of transmission of RF energy into the transmission medium (for example, the atmosphere), reception of reflected energy, (also known as backscatter or return energy), and analysis of the received energy to determine the presence and possibly characteristics of the detected object(s). Each type of radar system is optimized for the targets sought to be detected by the radar.
For example, weather radar systems are tailored to detect airborne precipitation, known in the art as hydrometeors. Many weather radars operate in the radar frequency bands and wavelengths that require large antennas and may preferably be horizontally polarized to better detect falling hydrometeors. On the other hand, other radars, for example, air surveillance radars tend to be horizontally linearly, and may be circularly polarized in order to reject returns due to weather in the scan volume. Analysis of the return energy has long been performed by computer processors configured with software that is specifically developed to process the data represented by the received energy.
Being able to detect both weather and air targets meant multiple radar systems, i.e., a weather radar and a separate air surveillance radar, co-located at or near a site of interest. Each separate system would mean installation and operation of separate hardware (antenna, transmitter, receiver, computer processors, power supplies and displays), and separate software modules installed in those systems. This requires sufficient space to install and operate such hardware. It also results in increased costs for the hardware and its maintenance.
Multi-mode radars have been developed to provide detection capability of differing object types in a limited space. For instance, modern fighter aircraft (third generation and beyond) employ radars with multi-mode capability. There is an air-to-air radar for detection of airborne targets, and an air-to-ground radar for air-to-surface weapons targeting. The former may be pulsed, doppler, or pulsed-doppler, while the latter may be a pulse only synthetic aperture radar. There have been radars fielded that incorporate two antennae; one for search and detection, and the second for weapons guidance.
These radars however are only examples of achieving multi-mode capability in the confines of a small air platform. Heretofore, there is not a successfully deployed multi-mode radar for use at air fields, for example, that need a weather radar in addition to air surveillance capability.